Model-based procedure for scale-up of wet, overflow ball mills - Part II: Worked example

A new ball mill scale-up procedure is developed which uses laboratory data to predict the performance of MI-scale ball mill circuits. This procedure contains two laboratory tests. These laboratory tests give the data for the determination of the parameters of a ball mill model. A set of scale-up criteria then scales-up these parameters. The procedure uses the scaled-up parameters to simulate the steady state performance of the full-scale mill circuit. At the end of the simulation, the scale-up procedure gives the size distribution, the volumetric flowrate and the mass flowrate of all the streams in the circuit, and the mill power draw. A worked example shows how the new ball mill scale-up procedure is executed. This worked example uses laboratory data to predict the performance of a full-scale re-grind mill circuit. This circuit consists of a ball mill in closed circuit with hydrocyclones. The MI-scale ball mill has a diameter (inside liners) of 1.85m. The scale-up procedure shows that the full-scale circuit produces a product (hydrocyclone overflow) that has an 80% passing size of 80 mum. The circuit has a recirculating load of 173%. The calculated power draw of the full-scale mill is 92kW (C) 2001 Elsevier Science Ltd. All rights reserved.

Reliability of the Knee Examination in Osteoarthritis: Effect of Standardization

Objective. To assess the reliability of physical examination of the osteoarthritic (OA) knee by rheumatologists, and to evaluate the benefits of standardization. Methods. Forty-two physical signs and techniques were evaluated using a 6 X 6 Latin square design. Patients with mild to severe knee OA, based on physical and radiographic signs, were examined in random order prior to and following standardization of techniques. For those signs with dichotomous scales, agreement among the rheumatologists was calculated as the prevalence-adjusted bias-adjusted kappa (PABAK), while for the signs with continuous and ordinal scales, a reliability coefficient (R-c) was calculated using analysis of variance. A PABAK of >0.60 and an Re of >0.80 were considered to indicate adequate reliability. Results. Adequate poststandardization reliability was achieved for 30 of 42 physical signs/techniques (71%). The most highly reliable signs identified by physical examination of the OA knee included alignment by goniometer (R-c = 0.99), bony swelling (R-c = 0.97), general passive crepitus (R-c = 0.96), gait by inspection (PABAK = 0.78), effusion bulge sign (R-c = 0.97), quadriceps atrophy (R. = 0.97), medial tibiofemoral tenderness (R-c = 0.94), lateral tibiofemoral tenderness (R-c = 0.85), patellofemoral tenderness by grind test (R-c = 0.94), and flexion contracture (R-c = 0.95). The standardization process resulted in substantial improvements in reliability for evaluation of a number of physical signs, although for some signs, minimal or no effect of standardization was noted. After standardization, warmth (PABAK = 0.14), medial instability at 30degrees flexion (PABAK = 0.02), and lateral instability at 30degrees flexion (PABAK = 0.34) were the only 3 signs that were highly unreliable. Conclusion. With the exception of physical examinations for instability, a comprehensive knee examination can be performed with adequate reliability. Standardization further improves the reliability for some physical signs and techniques. The application of these findings to future OA studies will contribute to improved outcome assessments in OA.